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一、前言从断裂力学的观点来看,材料的疲劳裂纹扩展门坎值(以下简称门坎值)△K_(th),是一个在工程上有着重要意义的指标。它表明,一个带裂纹的构件在交变载荷作用下,其裂纹是否会扩展、构件是否会损坏的限值。从这一定义知道,裂纹前端的应力强度因子幅值△K大于门坎值△K_(th)时,裂纹将发展,并导致构件损坏;若△K值小于△K_(th),则裂纹将不会发展,构件可安全运用。因此,准确而又快速地测定工程材料的门坎值,是一项有迫切意义的工作。目前,国内常用的测定材料门坎值的方法有两种,即实测法和增K(应力强度因子)倒推法,这两种方法均存在费时的缺点,测
I. Introduction From the fracture mechanics point of view, the material fatigue crack growth threshold (hereinafter referred to as the threshold value) △ K_ (th), is an engineering significance of the indicators. It shows whether a cracked component will expand under the alternating load and whether the component will be damaged or not. From this definition, we know that the crack will develop when the amplitude of the stress intensity factor △ K at the front of the crack is greater than the threshold value △ K th (th), and lead to the damage of the component. If △ K is less than △ K th, the crack will not Will develop, components can be safely used. Therefore, accurate and rapid determination of the threshold value of engineering materials is an urgent task. At present, there are two methods commonly used to determine the threshold value of materials in China, namely, the real measurement method and the K (stress intensity factor) pushback method, both of which have time-consuming disadvantages.